Noise suppression in a hybrid fiber coaxial network

ABSTRACT

A coupling device for use in a hybrid fiber coaxial (HFC) network may be configured to disable an upstream path through it when there is only noise incident on the upstream path, and enable the upstream path through it when a desired transmission from a cable modem downstream of the coupling device is incident on the upstream path. The coupling device may be a trunk amplifier, a distribution amplifier, a splitter, or the like. The coupling device may comprise a single upstream interface coupled to a plurality of downstream interfaces. The enabling and/or disabling may be in response to a signal strength indicated by the SSI being below a threshold and/or in response to one or more control messages indicating whether any downstream cable modem is, or will be, transmitting.

PRIORITY CLAIM

This patent application is a continuation of U.S. patent applicationSer. No. 13/948,417 now U.S. Pat. No. 9,043,855, which makes referenceto, claims priority to and claims benefit from United States ProvisionalPatent Application Serial No. 61/674,737 titled “Method and System for aNoise Suppression in a Cable Television Network” and filed on Jul. 23,2012, now expired.

The entirety of the above-mentioned application is hereby incorporatedherein by reference.

INCORPORATION BY REFERENCE

This application also makes reference to:

-   United States Patent Application Publication No. 2013/0094416 titled    “Method and System for Client-Side Message Handling in a Low-Power    Wide Area Network,” and filed on Jul. 19, 2012;-   United States Patent Application Publication No. 2013/0097240 titled    “Method and System for Server-Side Message Handling in a Low-Power    Wide Area Network,” and filed on May 31, 2012;-   U.S. Pat. No. 8,711,750 titled “Method and System for a Low-Power    Client in a Wide Area Network,” and filed on Jul. 19, 2012;-   U.S. Pat. No. 8,687,535 titled “Method and System for Server-Side    Handling of a Low-Power Client in a Wide Area Network,” and filed on    Jul. 19, 2012;-   United States Patent Application Publication No. 2014/0022926 titled    “Method and System for a High Capacity Cable Network,” and filed on    Jul. 23, 2013; and-   United States Patent Application Publication No. 2014/0022943 titled    “Method and System for Service Group Management in a Cable Network,”    and filed on Jul. 23, 2013.

The entirety of each of the above-mentioned applications is herebyincorporated herein by reference.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to cable televisionnetworks. More specifically, certain embodiments of the invention relateto a method and system for noise suppression in a cable televisionnetwork.

BACKGROUND OF THE INVENTION

Convention cable television networks can be inefficient and haveinsufficient capacity. Further limitations and disadvantages ofconventional and traditional approaches will become apparent to one ofskill in the art, through comparison of such systems with some aspectsof the present invention as set forth in the remainder of the presentapplication with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method is provided for noise suppression in a cabletelevision network, substantially as shown in and/or described inconnection with at least one of the figures, as set forth morecompletely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram of an example cable/DOCSIS network.

FIGS. 2A-2C depict example cable television networks comprising couplingdevices operable to reduce noise in a cable/DOCSIS HFC network.

FIGS. 3A-3C illustrate exemplary implementations of a coupling devicethat is operable to reduce noise in a cable/DOCSIS HFC network.

FIG. 4A is a flowchart illustrating an example process for controllingnoise in a cable/DOCSIS HFC network.

FIG. 4B is a flowchart illustrating an example process for controllingnoise in a cable/DOCSIS HFC network.

FIG. 5 shows a cable/DOCSIS HFC network comprising passive couplingdevices that reduce noise in a network.

DETAILED DESCRIPTION OF THE INVENTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. As another example,“x, y, and/or z” means any element of the seven-element set {(x), (y),(z), (x, y), (x, z), (y, z), (x, y, z)}. As utilized herein, the term“exemplary” means serving as a non-limiting example, instance, orillustration. As utilized herein, the terms “e.g.,” and “for example”set off lists of one or more non-limiting examples, instances, orillustrations. As utilized herein, circuitry is “operable” to perform afunction whenever the circuitry comprises the necessary hardware andcode (if any is necessary) to perform the function, regardless ofwhether performance of the function is disabled, or not enabled, by someuser-configurable setting.

FIG. 1 is a diagram of an example cable/DOCSIS network. The examplenetwork comprises a cable modem termination system (CMTS) 102, a fibernode 104, amplifiers 106 ₁-106 ₃, a directional coupler 108, splitters110 ₁-110 ₃, and cable modems (CMs) 112 ₁-112 ₅.

The CMTS 102 may comprise circuitry operable to manage connections tothe CMs 112 ₁-112 ₅. This may include, for example: participating inranging operations to determine physical layer parameters used forcommunications between the CMTS 102 and CMs 112 ₁-112 ₅; forwarding ofdynamic host configuration protocol (DHCP) messages between a DHCPserver and the CMs 112 ₁-112 ₅; forwarding of time of day messagesbetween a time of day server and the CMs 112 ₁-112 ₅; directing oftraffic between the CMs 112 ₁-112 ₅ other network devices (e.g.,Ethernet interfaces of the CMTS 102 may face the Internet, Optical RFinterfaces of the CMTS 102 may face the CMs, and the CMTS may directtraffic between and among the Ethernet and Optical RF interfaces); andmanaging registration of the CMs 112 ₁-112 ₅ to grant the cable modemsnetwork (e.g., Internet) access. The registration process for a CM 112may comprise the CM 112 sending a registration request along with itsconfiguration settings, and the CMTS 102 accepting or rejecting thecable modem based on the configuration settings. The registrationprocess may additionally comprise an exchange of security keys,certificates, or other authentication information.

The fiber node 104 may comprise circuitry operable to convert betweenoptical signals conveyed via the fiber optic cable 103 and electricalsignals conveyed via coaxial cable 105.

Each of the amplifiers 106 ₁-106 ₃ may comprise a bidirectionalamplifier which may amplify downstream signals and upstream signals,where downstream signals are input via upstream interface 107 a andoutput via downstream interface 107 b, and upstream signals are inputvia downstream interface 107 b and output via upstream interface 107 a.The amplifier 106 ₁, which amplifies signals along the main coaxial“trunk,” may be referred to as a “trunk amplifier.” The amplifiers 106 ₂and 106 ₃, which amplify signals along “branches” split off from thetrunk, may be referred to as “branch” or “distribution” amplifiers.

The directional coupler 108 may comprise circuitry operable to directdownstream traffic incident on interface 109 a onto interfaces 109 b and109 c, and to direct upstream traffic incident on interfaces 109 b and109 c onto interface 109 a. The directional coupler 108 may be a passivedevice.

Each of the splitters 110 ₁-110 ₃ may comprise circuitry operable tooutput signals incident on each of its interfaces onto each of its otherinterfaces. Each of the splitters 110 ₁-110 ₃ may be a passive device.

Each of the cable modems (CMs) 112 ₁-112 ₅ may comprise circuitryoperable to communicate with, and be managed by, the CMTS 1102 inaccordance with one or more standards (e.g., DOCSIS). Each of the CMs112 ₁-112 ₅ may reside at the premises of a cable subscriber.

The components (including, fiber optic cables, coaxial cables,amplifiers, directional couplers, splitters, and/or other devicesbetween the CMTS and the CMs may be referred to as a hybrid fibercoaxial (HFC) network. Any of the amplifiers, directional couplers, andsplitters may be referred to generically as a coupling device.

Referring to FIG. 2A, there is again shown the cable network of FIG. 1.In FIG. 2, however, in FIG. 2A additional details of the amplifiers 106₁-106 ₃ are shown. Specifically, each of the amplifiers 106 comprises adownstream gain element 220 and an upstream gain element 222. A gain ofeach of the upstream gain elements 222 may be dynamically controlled. Inthe scenario depicted in FIG. 2A, upstream gain element 222 of each ofamplifier 106 ₁ and 106 ₃ are “on” (e.g., set to a value greater than 1)whereas a gain of upstream gain element 222 of amplifier 106 ₂ is “off”(e.g., set to zero or to a value less than 1). Assuming for illustrationpurposes that, at the time instant shown, the signal from CM 112 ₁ is adesired signal but the signals from CMs 112 ₂-112 ₅ are noise, theconfiguration of FIG. 2A provides the advantage that interference withthe desired signal from CMs 112 ₄ and 112 ₅ is substantially reduced ascompared to gain element 222 of amplifier 1062 being “on.” Nevertheless,the configuration of FIG. 2 does not reduce the interference with thedesired signal cause by noise from CMs 112 ₂ and 112 ₃.

Referring to FIG. 2B, a network configuration is shown that providesadditional reductions in interference relative to the network of FIG.2A. In FIG. 2B, the passive splitters 110 ₁-110 ₃ have been replaced byactive coupling devices 210 ₁-210 ₃. Each coupling device 210 comprisesone upstream gain element 222 and one downstream gain element 220 perdownstream interface of the coupling device 210 (for simplicity ofillustration each of the coupling devices is shown as having twodownstream interfaces). An example scenario illustrating the reducedinterference in the configuration of FIG. 2B is shown in FIG. 2C.

Referring to FIG. 2C, again assuming that CM 112 ₁ is transmitting andthe other CMs 112 ₂-112 ₅ are emitting only noise during the timeinstant shown, turning off gain element 222 ₂ of device 210 reducesinterference caused by noise from CMs 112 ₂ and 112 ₃. Similarly, inanother time instant where CM112 ₂ is transmitting a desired signal(i.e., is the “talker” as a result of being granted access to the mediumby the CMTS), then turning off all gain elements 222 other than 222 ₁ ofdevice 210 ₃ may provide for low interference with the desired signaltransmitted by CM 112 ₂.

FIGS. 3A-3C illustrate exemplary implementations of a coupling devicethat is operable to reduce noise in a cable/DOCSIS HFC network. Each ofthe implementations 400, 404, and 408 shown in FIGS. 3A-3C,respectively, may represent any of the amplifiers 106 ₁-106 ₃ and/or aportion of any of the devices 210 _(1—) 210 ₃.

Referring to FIG. 3A, the device 400 comprises a signal strengthindicator (SSI) 402 operable to detect signal strength of signalsincident on the downstream interface 401 b. In an exampleimplementation, signal strength of upstream signals incident on thedownstream interface 401 b may be used for controlling the gain of gainelement 222 ₁ as described below with reference to FIG. 4A. In thismanner, the device 400 may be operable to autonomously enable anddisable an upstream path through the device 400 (the path through gainelement 222) without the device 400 requiring additional circuitry (andthus complexity) as is present in the implementations of FIGS. 3B and3C. For example, the SSI 402 may comprise entirely combinatorial logicor may comprise entirely passive elements (e.g., a simple envelopedetector).

Referring to FIG. 3B, the implementation 404 comprises receiver circuit406 which may be operable to receive instructions transmitted (e.g., byCMTS 102 and/or by one or more of CMs 112 ₁-112 ₅) in accordance with acommunication protocol selected by the operator of the HFC network. Inan example implementation, the protocol may be a relatively-simpleout-of-band physical layer signaling protocol. In another exampleimplementation, the receiver 406 may be operable to implement a protocolstack (e.g., simple network management protocol stack). In anotherexample implementation, the receiver 405 may be operable to implement asufficient portion of the DOCSIS protocol stack that it is operable tomonitor for, and upon detecting, inspect DOCSIS MAC management messages(e.g., upstream channel descriptors (UCDs), upstream bandwidthallocation messages (MAPs), and/or the like).

Referring to FIG. 3C, the implementation 408 comprises a transceivercircuit 410 which may be operable to both transmit and receive (e.g.,for communicating with CMTS 102 and/or by one or more of CMs 112 ₁-112₅) in accordance with a communication protocol selected by the operatorof the HFC network. In an example implementation, the protocol may be arelatively-simple out-of-band physical layer signaling protocol. Inanother example implementation, the transceiver 410 may be operable toimplement a protocol stack (e.g., simple network management protocolstack).

While the implementation of FIG. 3A has the advantage of simplicity bothin terms of the complexity of the circuitry and in terms of managementprotocols, the example implementations of FIGS. 3B and 3C may have theadvantage of controlling gain elements 222 based on higher-layerintelligence (e.g., determined and communicated by CMTS 102). Forexample, gain elements may be controlled based on the service group(s)downstream from them. To illustrate, referring back to FIG. 2A andassuming that CMs 112 ₁-112 ₃ are part of a first service group and CMs112 ₄ and 112 ₅ are part of a second service group, a control messagemay be sent to all receivers 406/410 in the network informing them as towhich timeslots will be used by the first service group and whichtimeslots will be used by the second service group. Using thisinformation, the receivers 406/410 can then enable and disable theirrespective gain elements 222 based on the current time, rather thanhaving to wait and sense signal strength. This may reduce or eliminatethe need for additional preambles or other physical layer signaling thatmay be required for device 400 to prevent interference from leakingthrough a not-yet-disabled upstream path, and/or to prevent desiredsignals from colliding with a not-yet-enabled upstream path. Suchservice-group-based control of gain elements 222 may be particularlyuseful where the CMs 112 ₁-112 ₅ have been assigned to service groupsbased on their location within the HFC network (e.g., where a particulardevice 406/410 handles only CMs of a particular service group, anupstream path through that particular device 406/410 can be disabledwhenever the talker is not part of that particular service group).

Similar to the service-group based control of gain elements 222, anotherexample implementation may perform CM based control of gain elements222. That is, each gain element 222 may be enabled based on whichparticular CM that is transmitting (or will be transmitting). Theservice group based implementation may use a look-up table (e.g., storedin receiver 406 or 410) that indicates which element(s) 222 should beenabled for each service group. Similarly, the CM based implementationmay use a look-up table that indicates which element(s) 222 should beenabled for each CM.

In an example implementation, the CMTS 104 may determine which of theCMs 112 ₁-112 ₅ are handled by which of the devices 106 ₁-106 ₃ and/orby which of the devices 210 ₁-210 ₃. This determination may be based onchannel sounding techniques. In another example implementation, the CMTS102 may communicate with a server that stores subscriber informationthat associates the CMs 112 ₁-112 ₅ with their respective geographiclocations, such that the locations of the CMs 112 ₁-112 ₅ within the HFCnetwork can be determined, and, in turn, which device(S) 106 and/or 210amplifier(s) serve(s) which of the CMs 112 ₁-112 ₅ may be determined.

FIG. 4A is a flowchart illustrating an example process for controllingnoise in a cable/DOCSIS HFC network. The process begins with block 4020in which a noise-controlling coupling device (e.g., 106 or 210) isinstalled in a HFC network. In block 4040, the coupling device monitorsone or more characteristic(s) of an upstream signal incident on one ormore of its downstream interfaces. The monitoring may comprise, forexample, measuring average signal strength, peak-to-average signalstrength, burst length, and/or any other suitable characteristics of theupstream signal(s). In block 4060, the coupling device determines, basedon the characteristic(s) of the signals, whether the incident signalcomprises a desired signal or whether the incident signal consistsentirely of noise. If the signal is all noise, then in block 4080 acorresponding upstream path through the coupling device is disabled. Ifthe signal contains a desired signal, then in block 4100 thecorresponding path through the coupling device is enabled. The block4060 and either 4080 or 4100 may be performed for each downstreaminterface of the coupling device.

FIG. 4B is a flowchart illustrating an example process for controllingnoise in a cable/DOCSIS HFC network. The process begins with block 422in which a noise-controlling coupling device (e.g., 106 or 210) isinstalled in a HFC network. In block 424, a receiver of the couplingdevice listens for messages that provide instructions as to whichupstream paths to enable and which to disable. In an exampleimplementation, the receiver may listen for management messagesspecified in an applicable standard (e.g., MAP, UCD, and/or othermessages specified in a DOCSIS standard). In an example implementation,the receiver may listen for control messages sent for the specificpurpose of controlling gain elements in coupling devices throughout aHFC network. The control messages may be in accordance with a protocolspecifically designed for such management or may be in accordance with amore general network management protocol such as SNMP. In block 426, inresponse to the coupling device detecting a management message, it mayenable one or more of its upstream paths and/or disable one or more ofits upstream paths.

FIG. 5 shows a cable/DOCSIS HFC network comprising passive couplingdevices that reduce noise in a network. Shown is the example network ofFIG. 1, but the example network additionally comprises coupling devices502 ₁-502 ₅. An example implementation of the devices 502 is shown andcomprises a signal strength indicator (SSI), a circulator 506, and aswitch 508.

As downstream traffic enters a device 502 via upstream interface 501 a,the circulator 506 directs the downstream traffic out to interface 501b. As upstream traffic enters the device 502, the circulator 506 directsit to the signal path comprising switch 508. If switch 508 is open, theupstream path is prevented from getting onto interface 501 a. The switch508 may be opened and closed in any of the manners discussed aboveregarding controlling gain of gain element 222. For example, the switch508 may be opened and closed based on signal strength measured by SSI402, as shown.

Although, the coupling devices 502 are shown as having a singledownstream port, they may have any number of downstream interfaces(e.g., two downstream interfaces) and may be used in much the samemanner as devices 210 shown in FIGS. 2B and 2C.

In an example implementation of this disclosure, a coupling device(e.g., 106, 110, or 502) for use in a hybrid fiber coaxial (HFC) networkmay be configured to disable an upstream path through it (e.g., pathincluding a gain element 222 or switch 508) when there is only noiseincident on the upstream path, and enable the upstream path through itwhen a desired transmission from a cable modem downstream of thecoupling device is incident on the upstream path. The coupling devicemay be a trunk amplifier (e.g., 106 ₁), a distribution amplifier (e.g.,106 ₃), a splitter (e.g., 210 ₁), or the like. The coupling device maycomprise a single upstream interface (e.g., 209 a) coupled to aplurality of downstream interfaces (e.g., 209 b). The coupling devicemay comprise a signal strength indicator (SSI) (e.g., 402). Thedisabling may be in response to a signal strength indicated by the SSIbeing below a threshold. The enabling may be in response to the signalstrength indicated by the SSI being above the threshold. The couplingdevice may be operable to detect control messages in the HFC network.The disable may be in response to one or more control messages (e.g.,exchanged in accordance with a coupling device control protocol)indicating that a cable modem downstream of the coupling device is, orwill be at some determined time in the future, transmitting. The enablemay be in response to one or more control messages (e.g., exchanged inaccordance with a coupling device control protocol) indicating that acable modem downstream of the coupling device is, or will be at somedetermined time in the future, transmitting. The control message mayindicate a service group of which a cable modem is, or will be at somedetermined time in the future, transmitting. The coupling device maycomprise a pair of cross-coupled gain elements (e.g., 220 and 222) foreach downstream interface. The coupling device may comprise a switchingelement (e.g., 508) and a circulator (e.g., 506). The circuitry maycomprise a switch and the disabling may comprise opening the switch. Thecircuitry may comprise an amplifier and the disabling may comprisereducing a gain of the amplifier.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform processes as described herein.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A system comprising: a coupling device for use in a hybrid fibercoaxial (HFC) network, said coupling device configured to: disable anupstream path through said coaxial portion of said HFC network whenthere is only noise incident on said upstream path; and enable saidupstream path through said coaxial portion of said HFC network when adesired transmission from a cable modem downstream of said couplingdevice is incident on said upstream path.
 2. The system of claim 1,wherein said coupling device is a trunk or distribution amplifier. 3.The system of claim 1, wherein said coupling device comprises a singleupstream interface coupled to a plurality of downstream interfaces. 4.The system of claim 1, wherein: said coupling device comprises a signalstrength indicator (SSI); said disable is in response to signal strengthindicated by said SSI being below a threshold; said enable is inresponse to said signal strength indicated by said SSI being above saidthreshold.
 5. The system of claim 1, wherein: said coupling device isoperable to detect control messages in said HFC network; each of saiddisable and said enable is in response to a respective one of saidcontrol messages.
 6. The system of claim 5, wherein a first one of saidcontrol messages indicates a service group of said cable modem that is,or will be at some determined time in the future, transmitting.
 7. Thesystem of claim 1, wherein said coupling device comprises a pair ofcross-coupled amplifiers for each downstream interface.
 8. The system ofclaim 1, wherein said coupling device comprises a switching element anda circulator.
 9. The system of claim 1, wherein said circuitry comprisesa switch and said disabling comprises opening said switch;
 10. Thesystem of claim 1, wherein said circuitry comprises an amplifier andsaid disabling comprises reducing a gain of said amplifier.
 11. A methodcomprising: performing in a coupling device of a hybrid fiber coaxial(HFC) network: disabling an upstream path through said coaxial portionof said HFC network when there is only noise incident on said upstreampath; and enabling said upstream path through said coaxial portion ofsaid HFC network when a desired transmission from a cable modemdownstream of said coupling device is incident on said upstream path.12. The method of claim 11, wherein said coupling device is a trunk ordistribution amplifier.
 13. The method of claim 11, wherein saidcoupling device comprises a single upstream interface coupled to aplurality of downstream interfaces.
 14. The method of claim 11, wherein:said coupling device comprises a signal strength indicator (SSI); saiddisabling is in response to signal strength indicated by said SSI beingbelow a threshold; said enabling is in response to said signal strengthindicated by said SSI being above said threshold.
 15. The method ofclaim 11, wherein: said coupling device is operable to detect controlmessage in said HFC network; each of said disabling and said enabling isin response to a respective one of said control messages.
 16. The methodof claim 15, wherein a first one of said control messages indicates aservice group of said cable modem that is, or will be at some determinedtime in the future-transmitting.
 17. The method of claim 11, whereinsaid coupling device comprises a pair of cross-coupled amplifiers foreach downstream interface.
 18. The method of claim 11, wherein saidcoupling device comprises a switching element and a circulator.
 19. Themethod of claim 11, wherein said circuitry comprises a switch and saiddisabling comprises opening said switch;
 20. The method of claim 11,wherein said circuitry comprises an amplifier and said disablingcomprises reducing a gain of said amplifier.